The voracious fish is the focus of a lawsuit brought by five Great Lakes states to force the federal government to close Chicago-area shipping locks in an effort to keep the carp out of Lake Michigan.

The 30-pound silver carp that leapt from the water last week and knocked a kayaker out of a 340-mile race down the Missouri River is a reminder of what's at stake Tuesday when the Asian carp debate returns to court in Chicago.

Five Great Lakes states are suing the federal government to force closing of Chicago-area shipping locks as a last-ditch effort to keep the invasive species from entering Lake Michigan.

The anticipated three-day legal showdown begins Tuesday in federal court as attorneys from Michigan, Ohio, Pennsylvania, Wisconsin and Minnesota will try to convince U.S. District Judge Robert Dow that Asian carp pose such a grave threat to the Great Lakes that nothing short of an emergency shutdown of the system will stop them.

At a preliminary hearing last week, Michigan's Assistant Atty. Gen. Robert Reichel told Dow that the U.S. has reached a "biological tipping point" for invasive species threatening the Great Lakes. He said closing the locks, which open to regulate water levels and permit the passage of boats and ships, is perhaps the only way to keep Asian carp out of the Great Lakes and protect its estimated $7-billion annual commercial and recreational fishing industry.

Attorneys representing the U.S. Army Corps of Engineers, which operates the locks, argued the federal government has spent millions of dollars to monitor and stop Asian carp on their march up the Illinois River. They say closing the locks may not be effective and could make the problem worse.

Business leaders in Illinois say closing locks in the waterway system, even for a short time, could deal a crippling blow to the shipping and boating industries, which help drive the state's economy. This case "is a tremendous risk for the city of Chicago and the region's economy, traffic congestion and flood control," said Jim Farrell of the Illinois Chamber of Commerce, which has fought to keep the locks open.

Asian carp, which have steadily moved up the river toward Chicago since the 1990s, present a challenge for scientists and fish biologists. The fish are aggressive eaters, consuming as much as 40% of their body weight a day in plankton, and frequently beat out native fish for food, threatening those populations.

They are also prolific breeders with no natural predators in the U.S. The fish were imported in the 1970s to help wastewater treatment facilities in the South keep their retention ponds clean. Mississippi River flooding allowed the fish to escape and then move into the Missouri and Illinois rivers. Some species can grow to more than 100 pounds.

Silver carp, one species of Asian carp, are also notorious for leaping from the water. The fish have injured boaters, anglers and water-skiers in many states. That happened last week, when one of the favorites in a kayak race across Missouri was smacked in the head by a carp weighing an estimated 30 pounds.